// 云函数入口文件
const cloud = require('wx-server-sdk')

cloud.init()
const db = cloud.database()
const _ = db.command
const $ = _.aggregate
// 云函数入口函数
exports.main = async (event, context) => {
  return await db.collection('comments').aggregate()
  .project({
    _id: 1,
    _openid:1,
    comment:1,
    postid:1,
    createTime:1,
    time:1,
  })
  .sort({
    createTime: -1
  })
  .lookup({
    from: 'users',
    localField: '_openid',
    foreignField: '_openid',
    as:'commentedBy'
  })
  .match({
   postid: event.postid 
  })
  .skip(event.skiplength)
  .limit(25)
  .end()
}